Is there a way to get the process model ID from its UUID?...

In that case then, I think you just need to use the process model details by uuid plugin function to get the pmid at call time - would this work within the configuration of the start process node?

Mike, using the Process Model Details by UUID plugin function would work, but since the data is returned in a formatted string, rather than in a dictionary, I'd need to extract the ID from it using string parsing. This seems like a really round-about and potentially error prone method of obtaining the ID. I could look into writing a simple plugin that gets it, if one doesn't already exist.

Also, I tested the Start Process Node with an integer ID, and that does work for calling the matching process with that ID.

I agree with your critique regarding the data returned by the plugin expression, and for that reason I've already written an expression rule in the past that does the needed parsing and passes back a dictionary. I can post it tomorrow if you need, as I'm travelling today.

Edit: I'm back today, so here's the expression rule I mentioned in case anyone would like to use it.

=/*  GLBL_processModelDetailsByUUID  */

with(
  local!rawText: if(
    rule!APN_isBlank(ri!uuid),
    " ",
    getprocessmodeldetailsbyuuid(ri!uuid)
  ),

  local!type: extract(local!rawText, "Type:", "," ),
  local!nameList: trim( split( extract( rawText, "Name: [", "]" ), "," )),
  local!nameArray: apply( rule!GLBL_returnLanguageNamePair, local!nameList ),
  local!id: extract( local!rawText, "Id:", ", UUID" ),
  local!uuid: extract( local!rawText, "UUID:", ", Creator" ),
  local!creator: extract( local!rawText, "Creator: ", ", Last" ),
  local!lastModifiedBy: extract( local!rawText, "Last Modified by: ", ", Parent"),
  local!parent: extract( local!rawText, "Parent: ", ", Parent Id:" ),
  local!parentId: tointeger( extract( local!rawText, "Parent Id: ", "," )),
  local!location: extract( local!rawText, "Location: ", ", Is" ),
  local!isPublic: extract( local!rawText, "IsPublic: ", ", Created" ) = "true",
  
  /* note: for the latest versions of the content details by uuid plugin, 
    the following lines can have the expression rule call replaced with 
    a simple "todatetime()" function, as the plugin was upgraded to 
    return a more standard datetime string after this handler rule was
    originally written. */
  local!createdOn: rule!GLBL_dateTimeStringToDatetime(extract( local!rawText, "Created on: ", ", Last" )),
  local!lastModifiedOn: rule!GLBL_dateTimeStringToDatetime(extract( local!rawText & "END", "Last Modified on: ", "END" )),
  
  {
    type: local!type,
    primaryName: property(index(local!nameArray, 1, ""), "name", ""),
    nameArray: local!nameArray,
    id: local!id,
    uuid: local!uuid,
    creator: local!creator,
    lastModifiedBy: local!lastModifiedBy,
    parent: local!parent,
    parentId: local!parentId,
    location: local!location,
    isPublic: local!isPublic,
    createdOn: local!createdOn,
    lastModifiedOn: local!lastModifiedOn
  }
)

/* developed by: Mike Schmitt */